Potential relay



April 22, 1958 D. E. MoRAN 2,831,934

POTENTIAL RELAY Filed March 2l, 1955 /n l/en tor' 5oz? iT/Vorw?,

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POTENTIAL RELAY Don E. Moran, Morrison, Ill., assignor to General Electric Company, a corporationof New York Application MarchiZl, 1955, Serial No. 495,553 p 6 Claims. (Cl. 200--87) This invention relates to electricalapparatus, andmore particularly to an improved electromagnetic relay.

There are countlessapplications of electrical apparatus where it is required that a circuit be closed or opened in response to a predetermined condition. Such conditions may include, for instance, lthe potential across a' certain piece of apparatus, or the current therethrough. One instance of such a situation is wherea single phase alternating current electric motor is provided with a starting winding which is to be disconnected as the motor comes up to speed. If-means are provided to cause the starting winding to be disconnected in response'to a predetermined potential, the desired operation of the motor at all times is obtained. The conventionalmethod of obtaining the response is to utilize a predetermined potential or current to energize the electric coil of an electromagnet. A movable armature member is provided which, at a predetermined level of energization of the coil, is attracted toward a pole of the electromagnet. This movement is used to actuate contact means to open or close an electric circuit. As the level of enegrization of thecoil drops, the armature member is released and the Contact means returns-to its previous' position.

It is generally highly desirable in apparatus of this type that there bea relatively wide differential between the pick-up level of energization at which the armature member is attractedtoward the electromagn'et and the drop-out level of energization at'which the electromagnet is unable to hold the armature' member. In addition, in order to provide the apparatus with greater adaptability, it is desirable that the force causing the armature` member' to tend to vpull away fromv the field member, be adjustable. Adjustability is also'desirable'for the space between the armature member and the core member when' the armature memberis inits'open position becausel this space, or gap, is an' important factor in determining'at what energy levell the armaturemem'b'er will be attracted to the electromagnet;

Another importantfeature in electromagnetic relays destined for certain applications'y is to' insure that the relay willhave a repick-up voltage' substantially equal tothe calibrated voltage' of closing. By` repick-up is meant the voltage at vwhichfrthey armature can be pulled back toward the pole of the electrom'agnet immediately aftert hasbeen caused to move kaway therefrom. This becomesy especially important where the relay is used, asI described before, to'fcontrol the starting winding of a single phase motor: Such relays are generally arranged to open a Contactin the'circuit of the starting winding when the relay picks up and to close theicontact when the relayr drops out. Normally,'such a relay is so connected that whenf-thestartin'g winding has been de-energized the voltage across the relay drops substantially, but

remainsabove theflevel'at which the relay would drop out,` in order to prevent reenergization`l of ythe starting winding. However; if the motor should be stalled, the voltage across'the starting windingfwith only the main winding: energized'A .will decend to a value where it willy be United States Patent() t 2,831,934 Patented Apr, 22, 1958 l possible for the relay to dropout. starting winding will 'then be' re-energized and the voltage across it will immediately increase. If, under these conditions, the armature member of the relay is permitted to bounce or otherwise decrease the gap between it and the pole of the electromagnet below the normal gap when kthe karmature member is in its ordinary open position,

the eiectromagnet may be able to" pick' up the' armature member and thereby disconnect the startwinding of the motor. However, with the motor stalled, the motor speed will, of course, be'below that at which the' relay would ordinarily pick up and, the relay will drop out as soon as it picks up andy there' will result a lluttering action of the armature which will result' infL a burning of the contacts. This'situation is one which has arisen in recent years, and is generally tie'd to the` overload stalling of compressors, for instance, in roorn coolers.- It will be seen that if the repick-up voltage is maintained substantially thev same asi'the calibrated pick-up voltage,

there will be nofpossibility of the uttering action occurring under stalled rotor conditions.

The object of this invention,l therefore, is to'p'rovide an electromagnetic relay which will incorporate the desirable features set forth above. i

Further objects and advantages of this invention will become apparent and the invention will be better unde`r stood by reference to the following description and the accompanying drawing, and the features of novelty which characterize this invention will be pointed'k out with particularity in the claims annexed to and forming a part of this specification.

y This invention, in its broadest aspect, provides an electromagnetic relay which has'fa base member with an electromagnet securedthereto. Anarmature member of magnetic material is arranged in movable relation to a pole of the electromagnet so as to move toward it when a' predetermined amoun'd of tiuX is generated. The armature member is engaged by means which normally bias it 'away from the magnet pole, and means are secured to the base'to limit the movement of the'armature member away from fthe electromagnet under the inil'uence of the biasing means. Contact means are arranged independently of the armature member but so as toy be operable thereby when thearmature member ymoves toward the electromagnet. The biasing `rneans engaging the armature member preferably comprising a spring which .is so arranged that it will exert a progressively smallerbias on the armature member as it is moved toward the electromagnet. -It will be clear that such an arrangement will increase the'range between the level of energization of the coil ofthe electromagnet .which is necessary to pick up the armature, and the 'level oi energization of the coil at which theA armature will pull away from-r the magnet pole. In addition, the armaturememtromagnet once itis released without sacrificing the reliability of operation thereof.

in the drawing,

Figure l is a side view of the improved relay of this invention with the field member and armature member thereof separated; i

Figure 2 is a like view of the improvedf relay ofthis invention, partly broken away, after the armature niember has been picked up by the field member;

Figure 3 is a top view, partly broken away and partly in cross section, of the improved relay as set forth' in Figure l;

Figurefl is an exploded view in perspective of the base f member and the armature member of the improved relay;

and

In such a case, thek Figure is a fragmentary side view illustrating the improved relay with a modified contact arrangement.

Referring now to Figures l through 4 of the drawing,

cated by the numeral 1. The relay may be arranged on a base 2 formed of any desired insulating material, and provided with downwardly extending parts 3 which act as supports and raise the level of the base to provide room for a plurality of terminals 4, 5, 6, 7, and 8. As will be shown later, only terminals 4, 7, and 8 are utilized by the invention proper so that terminals 5 and 6 available for other connections as desired. A base member 9 of conductive magnetic material is secured to base 2 by any desired means. In the present embodiment, terminal 7 has been used as one point of securement, with the base member 9 being provided with an extension 10 having an opening 11 which is aligned with the opening of ter minal 7 so that the two may be secured together. For added rigidity, base member 9 may also be secured to base 2 by flange 12 having an opening 13 through which a member may `be inserted to secure base member 9 to base 2. As is best seen in Figure 4, base member 9 has an upwardly extending iat portion 14 provided with an opening 15.

An electromagnet generally indicated at 16 comprising a coil 19 surrounding an axial magnetic core 18 is secured to part 14 of member 9 by any desired mean-s such as a headed threaded member 17 extending through opening 15 and secured within core 18. An insulating board 21 covers the coil 19 at the secured end of the electromagnet 16, and another insulating board 22 covers the coil at the unsecured end of the electromagnet. An opening 23 is provided in board 22 for a magnet pole 24 of core 1S to extend therethrough. As is well known, improved results may be obtained by also providing a shading coil 25 in connection with the pole 24. The construction of the electromagnet 16 as set forth is well known in the art and has been fully described for better illustration of the invention. An electrical conductor 26 projects from coil 19 and may be connected, as by soldering or brazing as shown at 27, to a conductor 28 secured to terminal 8. A second wire 29 connects the other end of coil 19 to projection 30 on part 14 of member 9 which is particularly shaped to permit the welding, soldering, or brazing of the wire, as shown at 31. It will be recalled that member 9 is secured to base 2 in one location by means of terminal 7. It will now be apparent that an external source of electrical power may be connected to energize the coil 19 through the terminals 7 and 8.

Base member 9 is also provided with 'a pair of portions 32 and 33 which, as best seen in Figure 3, extend along the side ofheld member 16, and are, respectively, notched to form bearing surfaces 34 and 35 for an armature member 38. The provision of the bearing surfaces results in the formation of projections 36 and 37 at the end of parts 32 and 33 respectively. Base member thus also constitutes a path for magnetic flux between electromagnet 16 and armature member 38 and is often called a yoke member.

Armature member 38, formed of magnetic material, is

provided with a widened portion 39 having a pair of notches 40 and 41 provided on each side thereof respectively. Armature member 38 is assembled with its wide part 39 positioned between the projections 36 and 37 so that grooves 41 and 40 iit thereover respectively to prevent undesired lateral movement of the armature member 38. ln this manner the armature member is seated so that it is free to be moved pivotally with respect to parts 32 and 33 of member 9. Wide part 39 of armature member 3S is divided into two leg portions 42 and 43; leg 42 is longer than leg 43 and has a bent over end portion 44 angularly extending preferably at about a right angle to the armatures opposite end portion 52 in a direction away from parts 32 and 33 of member 9.

`having a groove 46 formed therein.

Protruding from one side of the bent over portion 44 of leg 42 there is provided a small extending portion 45 Part 14 is provided with an arm portion 47 extending in the same plane as part 14 and which has a plurality of grooves 48 formed therein. A helical spring 49 has one end 50 secured in one of the grooves-48 of arm 47 of member 9 and the other end 51 secured in groove 46 of extending portion 45 of arm 42, and thus extends transversely across and adjacent to the pivot of armature member 38. End 52 of armature member 38 is biased away from pole 24 of electromagnet 16 by the action of the helical spring 49 on extending portion 45.

In order to limit the movement of armature member 38 in response to the biasing action of spring 49, there is provided a screw member 53 which is threadedly mounted in an opening 54 near the base of part 33 of member 9. Secured to the surface of portion 44 of arm 42 byv any desired means, such as brazing or welding', are a at leaf spring 55 preferably made of some highly resilient material such as, for instance, bronze, and a flat armature stop member 66 preferably formed of some rigid material such as many of the steel alloys. As is best seen in Figure 3, spring 55 is arranged so that it will come in contact with the head 56 of screw 53 to limit the motion of armature member 38 in response to helical spring 49, and the welding together of spring 55 and armature stop member 66 as shown limits the flexing of spring 55. This arrangement also permits adjustment of the amount of gap between end 52 of armature 38 and pole 24 of electromagnet 16 by rotation of screw 53 in opening 54.

An arm 57 is formed extending substantially perpendicular to portion 14. Secured to the end of arm 57 by any preferred means is a contact arm 58 of spring material having a ilange 59 extending at right angles at the other end thereof. The end of flange 59 is again bent over as shown at 60, and a contact 61 is conductively secured to contact arm 58. A stationary contact 62 is firmly secured to the end of a stationary and rigid contact arm 63 which is secured to the base 2 at terminal 4 in conductive relation with the terminal by means of ilange 64.

The operation of the improved relay of this invention will now be described, and it will be assumed that terminals 7 and 8 have been connected to a source of electric power, and that terminals 4 and 7 are connected across the circuit which is to be controlled by the contacts 61 and 62. When the current through coil 19 rises to a predetermined value, pole 24 of the electromagnet will pick up armature member 38 and pull it down against the bias of spring 49 so that the armature member will snap 'against the pole 24. As this happens, portion 44 of leg 42 moves into contact with bent over portion 60 of contact arm 58. Contacts 61 and 62 are normally biased into engagement; however, when portion 44 contacts bent over portion 60, the contact arm 58 will be bent `backward and contact 61 will be moved away from contact 62. Thus, it will be seen that when the current through the coil 19 reaches a predetermined value contacts 61 and 62 will be separated.

When electromagnet 16 has pulled armature member 38 into contact with it against the action of spring 49, the spring will have been pulled to a position where it is almost in its on-center position and therefore exerts very little force tending to pull the armature member away from the electromagnet. The purpose of this is to increase the differential between the energization level of the coil at which the armature member 38 will be picked up and the level at which it will be released.

It will, of course, be clear that the space or gap between pole 24 and the armature member 38 is a controlling factor in the level of energization required to attract or pick up the armature 38. Thus, once the electromagnet v16 haspicked up the armature member 38 much less yand of contact arm 58, with from its dead center position.

The energization level y.at which the armature'member 38 is picked up yby the electromagnetlpis, as mentioned above, a function of the gap betweenendSZof the arma- .ture member and'pole 24 of the electromagnet. This gap may be adjusted by means of threaded vstop ymemberfSS. When vthe stop member is rotated it willmove .inor .out of openingf54 in member 9, and spring` 49 will cause=the armature member to followsuit, the motion ofthe armature member being limitedby the engagement of spring 55 with threaded 'member 53.y Thus, the morek deeply the'threaded member 53 is screwedinto opening .54, the

lgreater Awill be the gap between end 52 of the armature member and pole 24 ofthe electromagnet. The energization level at which-the armature member will drop out mayalso be varied by placing .end 50 ofspringv`49 inthe desired one of grooves 48. As the end 50 of the spring is moved into a different groove, the on-center position of the spring will be changed and, therefore, k,the `spring may be made to exert a pull, when the armature member has been picked up, which depends on which groove -48.is

used.

The relaywill maintain contacts 61 and,62 separated until the energization level of coil 19 drops below a value, predetermined by the positioning of spring 49, at which the armature member 38 will return jtothe dropped out position and portion 44 of arm 42 will cease to bear against bent over portion 60 of contact arm 58.y This will permit thespring like contact arm 58 to return to itsl `normal positionin whichcontact 61jisy permittedlto =re engage contact 62. It will be seenl that when armature member 33V starts-to drop out, itis being biased to the dropped out position bythecombinedaction of spring-49 gization in .coil .19 will increaseconsiderably assoon as` there isfengagement .between contacts 561 and S62. Thus, in such cases, although the energization level of the coil 19 become so low as to permit therelease of armature -member 3S, the consequent'release vand engagement of contacts 61 and 62 may cause the energization of the coil to increase to a value whichy is such that, if any bounceback of the armature member is permitted, the gap will become small enough .for the increased energization of the coil to cause pole 24 to pick up armature member 38. This in turn would open the contacts 61 and 62 which wouid then cause a decrease in the level of energization to the point where armature member 38 would drop out. The cycle would then repeat with ensuing damage to the contact mechanism and, quite possibly, tothe apparatus controlled by the relay. p

In order to prevent any substantial bounce-back of armature member 38 after it is opened, that is, to prevent a diminution of the gap to the point where the relay may be picked up again at a valuebelow the calibrated voltage,

y the threaded stopy member 53 and armature stop member 66 are relatively rigid while the leaf spring 55 isrelatively llexible. Itwould at first glance appear that if all were made rigid there would be no substantial bounce-back. While this is so, it has also been discovered that if all the parts are made rigid it is practically impossible to vprovide an accurate calibration of the energization level of coil 19 at which armature member 38 will be picked up.`

"therefore, this solution to the problem is not the best one' available. Experimentation has shownfthat the provision of the rigid armature stop member 66 together with the spring 49 constituting the' but which -also insures that the repick-up voltage will be f substantially the same as the icalibrated voltage.

For instance, it has been discovered that inta relay having housing dimensions (as shown by housing 165 in Figure l) of two -inches in length-by l and 27/fg2inches in height,

with a width(best seen in FigureB) of ,l and 3A inches, it lis l.desirable that the distance of bounce between the endof spring `S5 ,and armature stopfmember 66 when the armature membert38 is dropped `out kbe maintained between .020 inch and .045 inch. These `figures may be satisfactorily achievedby providing a ybronze spring havingia thickness of approximately .0085 inchin combination with .the rigid armature stop membert. These limits have been found to permit both asubstantially constant calibrated voltage and a frepick-up voltage having a value ofapproximately 90 to 95 ypercent of calibrated voltage. j

yItfwill be seen from the foregoing that thisinvention provides an electromagnetic relay in which the armature openfposition gap and .the armature ,drop-out value are both adjustable, and in which the repick-up voltage is .madesubstantially equal to the calibrated voltage without sacrificing the .consistency ofthe calibrated Voltage.

Referring now to yFigure 5, wherein likenumerals are used for likeparts, it will be seen that the relay of this invention may be `provided with` an extra contact mechanically and electrically secured to contact arm 58. An yextra contact arm 71 carrying contact 72 is secured in place by member 73 which in turn is secured to base 2 and varranged in electricalen'gagement with terminal 5. This arrangement is suitable in instances where the relay is used to sequence two circuits (such as, for'example, where it is desired that a particular circuit be completed after a motor is almost up to speed), and illustrates the rfact that the contactLarrangement set forth is not-necessarily a limiting factor for the'invention.

While this invention has been explained by describing aparticular embodiment thereof, it.y will bejapparentthat improvements and modifications may be made without departing from the scope ofthejinvention'as deinedin the appended claims.l

What I claimjas new and desire to secure by Letters Patent of the United Statesis:y

l. An electromagnetic relay comprising a base member, an electromagnet mounted on said base member, an arma ture .memberjpivotally mounted on said base member for movement toward said electromagnet, said armature member having end portions extending in angularly bent relation to one another on opposite sides of its pivotal mounting, and spring means connected to one end portion of said armature member to bias the opposite endportion away from said electromagnet, said spring means n extending transversely across and adjacent to the pivotal mounting of said armature and being arranged to move posite sides of its pivot with one end portion overlying a pole of saidelectromagnet, and spring means connected between the other end portion of said armature member and said base member tobias the overlying end portion away from said pole, said spring means extending transversely across A,and adjacent to the pivot of said armature and being arranged `to approach an on-center position relative to said pivot to decrease the biasing effect of said spring as said armature moves toward said electromagnet.

3. An electromagnetic relay comprising a magnetic base member, an electromagnet secured to said basemember, an armature member pivoted on said base member, said armature member having end portions extending in angularly bent relation to one another on opposite sides of its pivot with one end portion overlying said electromagnet, a helical tension spring connected between the other end portion of said armature member and said base member to bias the overlying end portion of the armature member away from said electromagnet, said helical spring extending transversely across and adjacent to said pivot and being arranged to approach said pivot as said armature memberl approaches said electromagnet thereby to exert a decreasing bias upon said armature member during said approach, and means for varying the location of the connection between the helical spring and the base member for adjusting the rate of decrease of said bias.

4. An electromagnetic relay comprising an electromagnet, a magnetic armature member mounted for movement toward said electromagnet under the magnetic attraction thereof, a pair of contacts operable by said armature member during its movmeent toward said electromagnet, spring means connected to said armature member for biasing said armature member away from said electromagnet, said spring means being constructed and arranged to exert a progressively smaller bias on said armature member as said armature member approaches said electromagnet, a leaf spring having one end connected to said armature member and one end free, a substantially rigid member having one end connected to said armature and its other end free and overlying the free end of said leaf spring in slightly spaced relation thereto, and stop means cooperating with said leaf spring and rigid member for limiting the movement of said armature member away from said electromagnet.

5. An electromagnetic relay comprising a magnetic base member, an electromagnet secured to said base member, a magnetic armature member pivoted onsaid base member for movement toward said electromagnet under the magnetic attraction thereof, contact means arranged to be opened by said armature during its movement toward said electromagnet, said armature member having a portion extending beyond its pivot, a helical tension spring connected between said extension portion and said base member for biasing said armature member away from said electromagnet, said helical spring extending transversely across and adjacent to said pivot and being arranged to approach its on-centerposition relative to said pivot when said armature member approaches said electromagnet thereby to decrease its biasing effect, a

leaf spring having-one end connected to said armature extension portion and one end free and stop means on saidbase member located to engage the free end of said leaf spring during the movement of said armature member away from-.said electromagnet.

6. An electromagnetic relay comprising a magnetic base member, an electromagnet secured to said base member, a magnetic armature member pivoted on said base member for movement toward said electromagnet under the magnetic attraction thereof, said armature member having a portion extending beyond its pivot, a pair of contacts arranged to be opened by said armature extension portion during the movement of said armature member toward said electromagnet, a helical spring connected between said extension portion and said base member for biasing said armature member away from said electromagnet, said helical spring being arranged to approach its on-center position relative to said pivot during approach of said armature member toward said electromagnet thereby to exert a progressively decreasing bias during said approach, a leaf spring having one end connected to said armature extension portion and one end free, stop means on said base member located to engage the free end of said leaf spring during the movement of said armature member away from said electromagnet, and a rigid member having one end connected to said armature extension portion and the other end free and overlying said leaf spring in slightly spaced relation thereto on the side thereof opposite said stop means to limit the movement of said armature member away from said electromagnet.

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